1. Field of the Invention
The invention relates to an image processing apparatus, a data processing method, and a printing system.
2. Description of Related Art
Generally, in order to obtain a high quality image, with respect to a photographic image, though a low resolution is acceptable, multi gradation is required. On the other hand, with respect to a character image, though a low gradation is acceptable, a high resolution is required. Accordingly, since the conditions required according to an attribute of an image is different, when a photographic image and a character image mix in one image, in data format of a same resolution or a same gradation, a high quality output image can not be obtained with respect to images of all attribute.
Conventionally, after discriminating image portions of the photograph and the character, different processes are performed to the photograph image and the character image respectively, and then the portion of the photographic image is made to low resolution and high gradation, the portion of the character image is made to the high resolution and the low gradation (e.g. see Japanese Patent Laid-Open No. 2000-242461, Japanese Patent Laid-Open No. 2004-320361).
However, as above mentioned, when the different processes are performed, since it is necessary to prepare the process compositions (hardware) of two systems corresponding to each process, the cost will increase.
Also, in the printer, and so on, it is constructed so as to store images to be output in a memory once, and read out the images from the memory in order. Though the compression process is performed to the image data so as to store as many image data as possible when storing and, the extension process is performed when outputting the images, a lossy compression is often utilized in order to increase the compression ratio of the image. However, when the same lossy compression is performed to the photographic image and the character image, the problem of losing the shape of the image portion of the character of the high resolution arises.
Accordingly, the countermeasure performing switching to a lossless compression for the character image portion that needs the high resolution or, the countermeasure performing the lossless compression to the photographic image and character image, etc. are taken.
However, in the former case, since the processing system for the lossless compression and the lossy compression is needed, the problem of high costs remains, while the control becomes complicated. Also, in the latter case, since the compression ratio becomes low in comparison with the lossy compression, there is the problem that the amount of image data to be stored in the printer is limited.